Every time I open a cut sheet, I save it to my "Catalogue and Data Sheets" Folder. If I've opened it once, there's about a 90% chance I'll need it again. Same with technical references, which go ion a different folder, a lot of which I've found in Eng-Tips.
It helps that File Explorer has a relatively good search module. Last week one of my coworkers wanted a reference on lateral supports on auger cast piles. I went to my main dumping ground ("Misc"), searched under "auger" and found an FHWA reference called "Drilled Shafts: Construction Procedures and LRFD Design Methods." The search function not only looks under the titles, but goes into the text of the document.
Believe me, it's not foolproof (please no comment), but it's bailed me out many times.